Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS5483568 A
Publication typeGrant
Application numberUS 08/335,384
Publication dateJan 9, 1996
Filing dateNov 3, 1994
Priority dateNov 3, 1994
Fee statusPaid
Publication number08335384, 335384, US 5483568 A, US 5483568A, US-A-5483568, US5483568 A, US5483568A
InventorsHiroyuki Yano, Katsuya Okumura
Original AssigneeKabushiki Kaisha Toshiba
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Pad condition and polishing rate monitor using fluorescence
US 5483568 A
Abstract
The invention is directed to a method for detecting the chemical mechanical polishing rate of a surface of a semi-conductor wafer. In chemical mechanical polishing, a slurry made of abrasive particles suspended in a chemically abrasive liquid is dispensed on the surface of a rotating polishing pad. The wafer to be polished is rotated and lowered into contact with the rotating polishing pad. The method includes directing an X-ray beam at an exposed surface area of the polishing pad, and detecting the intensity of the X-ray fluorescence which results from the beam illuminating the pad. Since both the CMP rate of removal of a wafer surface and the intensity of the X-ray fluorescence are functions of the density of the abrasive particles in the slurry, the CMP rate of removal can be expressed as a function of the density. Accordingly, the detected intensity of the X-ray fluorescence can be converted directly into the CMP rate, without interfering with the CMP process.
Images(5)
Previous page
Next page
Claims(23)
We claim:
1. A method for determining the polishing rate during abrasive polishing of the surface of a semi-conductor wafer in which a slurry including a liquid having a suspension of abrasive particles is sprayed upon a surface of a rotating polishing pad and a rotating semi-conductor wafer is brought into contact with the surface of the polishing pad, a portion of the surface of the pad exposed during contact, the method comprising:
directing electromagnetic radiation onto the exposed surface of the pad;
detecting the intensity of the electromagnetic radiation produced due to the electromagnetic radiation being directed upon the pad; and
converting the detected intensity into a polishing rate of removal of the surface of the wafer by utilizing a predetermined functional relationship between the intensity and the polishing rate.
2. The method recited in claim 1, the electromagnetic radiation comprising a beam which stimulates fluorescence in the slurry such that the intensity of the fluorescence is detected.
3. The method recited in claim 2, the beam comprising an X-ray beam and the fluorescence comprising X-ray fluorescence.
4. The method recited in claim 3, wherein, the abrasive polishing is chemical mechanical polishing.
5. The method recited in claim 4, wherein, the converting step includes utilizing a predetermined functional relationship between the intensity and the density of removed material from the wafer in the slurry and between the polishing rate and the density of removed materials in the slurry.
6. The method recited in claim 5, wherein, the removed material is SiO2.
7. The method recited in claim 4, wherein, the converting step includes utilizing a predetermined functional relationship between the intensity and the density of the abrasive particles in the slurry and between the polishing rate and density of abrasive particles in the slurry.
8. The method recited in claim 7, wherein, the abrasive particles are CeO2 and the liquid includes water.
9. The method recited in claim 3, wherein, the liquid includes water and the abrasive particles include CeO2.
10. A method for performing abrasive polishing comprising:
rotating a polishing pad and spraying a slurry including a liquid having a suspension of abrasive particles onto a surface of the pad;
rotating a semi-conductor wafer and bringing the rotating wafer into contact with the surface of the pad with an area of the surface of the pad exposed during contact;
directing electromagnetic radiation at the exposed surface area of the pad;
detecting the intensity of the electromagnetic radiation produced due to the electromagnetic radiation being directed upon the pad; and
converting the detected intensity into a polishing rate of removal of the surface of the wafer by utilizing a predetermined functional relationship between the intensity and the polishing rate.
11. The method recited in claim 10, the electromagnetic radiation comprising a beam which stimulates fluorescence in the slurry such that the intensity of the fluorescence is detected.
12. The method recited in claim 11, the beam comprising an X-ray beam and the fluorescence comprising X-ray fluorescence.
13. The method recited in claim 12, wherein, the liquid is water and the abrasive particles are CeO2.
14. The method recited in claim 12, wherein, the abrasive polishing is chemical mechanical polishing.
15. The method recited in claim 14, wherein, the liquid is a base.
16. The method recited in claim 14, wherein, the liquid is an acid.
17. An apparatus for determining the polishing rate during abrasive polishing of the surface of a semi-conductor wafer in which a slurry including a liquid having a suspension of abrasive particles is sprayed upon a surface of a rotating polishing pad and a rotating semi-conductor wafer is brought into contact with the surface of the polishing pad with a portion of the surface of the pad exposed during contact, the apparatus comprising:
means for directing electromagnetic radiation at the exposed surface of the pad;
means for detecting the intensity of the electromagnetic radiation produced due to the electromagnetic radiation being directed upon the pad; and
means for converting the detected intensity into a polishing rate of removal of the surface of the wafer.
18. The apparatus recited in claim 17, the electromagnetic radiation comprising a beam which stimulates fluorescence in the slurry such that the intensity of the fluorescence is detected.
19. The apparatus recited in claim 18, the beam comprising an X-ray beam and the fluorescence comprising X-ray fluorescence.
20. The apparatus recited in claim 19, said means for converting comprising means for storing a predetermined functional relationship between the intensity and the polishing rate, and means for applying the stored functional relationship to the detected intensity to determine the polishing rate.
21. The apparatus recited in claim 19, said means for directing comprising an X-ray tube and said means for detecting comprising an X-ray spectrometer.
22. A semi-conductor workpiece processing machine comprising:
a rotatable workpiece carrier, the rotating motion of the carrier being imparted to a workpiece carried thereon;
a rotatable polishing pad having an upper surface, said carrier and pad relatively movable to allow the workpiece to be brought into contact with said pad, said pad having a larger surface area than the workpiece so as to leave a surface of the pad exposed when the workpiece is in contact with said pad;
a slurry dispenser disposed to dispense slurry upon the upper surface of said pad;
an X-ray tube disposed to direct an X-ray beam at the exposed surface area of the pad;
an X-ray spectrometer, said spectrometer receiving the fluorescence reflected from the pad and determining the intensity thereof; and
means for converting the intensity of the reflected beam into a polishing rate of removal of the surface of the wafer and for providing a readout of the rate.
23. A method for performing abrasive polishing comprising:
rotating a polishing pad and spraying a slurry including a liquid having a suspension of abrasive particles onto a surface of the pad
rotating a semi-conductor wafer and bringing the rotating wafer into contact with the surface of the pad with an area of the surface of the pad exposed during contact;
directing electromagnetic radiation at the exposed surface area of the pad;
detecting the intensity of the electromagnetic radiation produced due to the electromagnetic radiation being directed upon the pad; and
terminating polishing when, after the detected intensity has first reached a substantially steady level, the intensity undergoes a reduction to a level which is less than a predetermined level.
Description
BACKGROUND OF THE INVENTION

1. Field of Invention

This invention is directed to a machine for polishing semi-conductor wafers, and more particularly, to a machine in which the polishing rate of the wafer surface and the condition of the polishing pad may be continually monitored.

2. Description of the Prior Art

Machines for preparing and fabricating semi-conductor wafers are known in the art. Wafer preparation includes slicing semi-conductor crystals into thin sheets, and polishing the sliced wafers to free them of surface irregularities, that is, to achieve a planar surface. In wafer fabrication, devices such as integrated circuits or chips are imprinted on the prepared wafer. Each chip carries multiple thin layers of conducting metals, semiconductors and insulating materials such as oxides, each of which may require polishing during fabrication. The polishing process may be accomplished by an abrasive slurry lapping process in which a wafer mounted on a rotating carrier is brought into contact with a rotating polishing pad upon which is sprayed a slurry of insoluble abrasive particles suspended in a liquid. Material is removed from the wafer by the mechanical buffing action of the slurry. The polishing step often includes a chemical mechanical polishing ("CMP") process. CMP is the combination of mechanical and chemical abrasion, and may be performed with an acidic or basic slurry. Material is removed from the wafer due to both the mechanical buffing and the action of the acid or base.

Devices for performing chemical mechanical polishing are known in the art, for example, U.S. Pat. No. 5,308,438 to Cote et al, incorporated by reference. The device of Cote includes a rotatable circular polishing platen having a circular polishing pad mounted thereon. A rotatable polishing head or carrier adapted for holding and rotating a workpiece such as a semi-conductor wafer is suspended over the platen. The carrier and platens are rotated by separate motors. A slurry dispensing tube is disposed over the polishing pad. In operation, a slurry, for example, an oxidizing agent such as iron nitrate dispersed in water with aluminum oxide particles suspended therein, is dispensed on the upper surface of the rotating polishing pad. The rotating wafer is brought into contact with the pad and is polished due to the mechanically abrasive action of the aluminum oxide particles and the chemically abrasive action of the oxidizing agent.

Chip fabrication requires the formation of layers of material having relatively small thicknesses. For example, a typical metal conducting layer will have a thickness on the order of 2,000-6,000 Å, and a typical insulating oxide layer may have a thickness on the order of 4,000 Å. The thicknesses will depend upon the function of the layer. A gate oxide layer may have a thickness of less than a hundred Å and a field oxide layer may have a thickness of several thousand Å. Nonetheless, the thickness of the layers must be formed within very strict tolerances, for example, 500 Å, in order to ensure that the desired operating parameters of the chip are achieved. Further, if the tolerances are not met, short circuits, or other defects which result in inoperative chips may result.

During chip fabrication, the layers are formed and then selected amounts of material must be removed without removing excess amounts of the underlying material in order to provide layers having thicknesses within the desired tolerances. One way to ensure that the selected amounts of material are removed in order to form layers having the desired thickness is by monitoring of the thickness of the layers during CMP. For example, the surface of the wafer may be physically examined by techniques which directly ascertain the dimensional and planar characteristics of the wafer, utilizing tools such as surface profilometers, ellipsometers or quartz crystal oscillators. However, use of these devices requires that the wafer be removed from the CMP apparatus. If the wafer does not meet specifications, it must be reloaded onto the apparatus and polished again. This process is time consuming and labor intensive, and decreases production efficiency. Further, if it is determined that too much material has been removed, the chip may have to be returned to the location at which the layers of material are applied, or may even be unusable.

A second way to ensure that desired amounts of material have been removed is by real time monitoring of the layer thickness as the wafer is being polished. Such a device is shown in U.S. Pat No. 5,240,552 to Yu et al, incorporated by reference, which makes use of acoustic waves which are directed at and reflected from the wafer during CMP. The reflected waves are detected and a determination is made of the total time the wave has travelled in the wafer. If the velocity of the waves through the water is known, the total thickness of the wafer and thus of a film layer thereon can be determined. However, the device of Yu et al requires complex circuitry for generating and detecting the acoustic wave. In particular, Yu makes use of a first piezoelectric transducer which is disposed between the wafer carrier and carrier pad in order to generate, in response to a voltage, an acoustic wave which will travel into and be reflected from a wafer, and a second similarly disposed piezoelectric transducer which converts the reflected acoustic wave back into a voltage. The transducers must be connected by conducting wires to an analyzing circuit, with the wires disposed in holes formed through the carrier. The fact that the Yu device includes components which are placed in physical contact with the moving parts of the CMP apparatus complicates the apparatus. Further, over time the effectiveness of the circuit may be deteriorated by the motion ;associated with polishing.

In principle, CMP also can be monitored by knowing with great certainty the CMP rate, that is, the rate at which material is being removed from the layer being polished. However, several factors affect the polishing rate. For example, during polishing the abrasive material of the slurry becomes embedded in the material of the polishing pad, reducing the density of material in the slurry. Further, the material being removed from the layer being polished becomes embedded in the pads, and the pads tend to become degraded over time during the polishing procedure. All of these factors affect the CMP rate and as a result, the rate is not constant throughout the usable life of a pad. In fact, the CMP rate is erratic even during CMP of one production lot of wafers and in some cases, CMP of a single wafer.

With reference to FIG. 1, a graph of the CMP rate versus total pad use time is shown for a single polishing pad. The graph of FIG. 1 is for oxide polishing with a slurry of Ceria (CeO2). The CMP rate of a layer of a CVD (chemical vapor deposition) oxide as expressed in the reduction of thickness of the layer per minute, is not stable, especially in the earlier stages of the usable life of a pad under approximately 600 minutes when the polishing rate increases greatly with continued use. Though the polishing rate is less erratic thereafter, it still varies above and below the rate of 7000 Å per minute. Furthermore, it is not possible to tell when the pad has worn out, which would cause the polishing rate to be reduced.

Accordingly, due to the non-stable CMP rate, in order to ensure that selected amounts of material are removed within acceptable tolerances using knowledge of CMP rate, it is necessary to measure the polishing rate before each production lot of wafers, and in some cases, where the tolerances are small, before CMP of each wafer. Such measuring requires that at least one otherwise usable production wafer be monitored during a test polishing procedure to make an accurate determination of the polishing rate. Thus, both time and a usable wafer must be wasted. As a result, the overall efficiency of production during use of CMP is compromised. Further, even with these procedures, it is not possible to determine the instantaneous CMP rate.

SUMMARY OF THE INVENTION

The present invention is directed to a method for detecting the polishing rate during abrasive polishing of the surface of a semi-conductor wafer in which a slurry including a liquid having a suspension of abrasive particles is sprayed upon a rotating polishing pad, and the rotating semi-conductor wafer is brought into contact with the polishing pad. A surface of the pad is exposed during contact. The method includes: directing electromagnetic radiation onto the exposed surface area of the pad; detecting the intensity of the electromagnetic radiation produced due to the electromagnetic radiation being directed upon the pad; and converting the detected intensity into a polishing rate of removal of the surface of the wafer by utilizing a predetermined known relationship between the intensity and the polishing rate.

In a further embodiment the electromagnetic radiation is a beam which stimulates fluorescence in the slurry and the intensity of the fluorescence is detected.

In a further embodiment the beam is an X-ray beam and the fluorescence is X-ray fluorescence.

In a further embodiment, the abrasive polishing is chemical mechanical polishing.

In a further embodiment, the invention is directed to an apparatus for detecting the polishing rate during abrasive polishing of the surface of a sem-iconductor wafer. The apparatus includes an X-ray tube for emitting X-rays towards the surface of a polishing pad, and an X-ray spectrometer for detecting the X-ray fluorescence from the surface of the pad.

The foregoing and other features, aspects and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the polishing rate as a function of total pad use time of a single polishing pad during CMP.

FIG. 2 is a perspective view of a CMP polishing apparatus including a polishing rate monitor according to the present invention.

FIG. 3 is a simplified side view of the apparatus shown in FIG. 2.

FIG. 4 is a simplified top view of the apparatus shown in FIG. 2.

FIG. 5 is a graph showing the CMP rate as a function of the Ceria density in the slurry.

FIG. 6 is a graph showing X-ray intensity as a function of Ceria density in the slurry.

FIG. 7 is a graph showing the CMP rate as a function of X-ray intensity.

FIGS. 8a and 8b are cross-sectional views of a wafer surface before and after polishing of a tungsten layer.

FIG. 9 is a graph representing the density of the tungsten in the slurry during polishing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIGS. 2-4, apparatus 1 including a CMP table and a CMP rate monitor according to the invention is shown. The inventive apparatus includes polishing platen 13 which is rotatable by platen drive motor 15 and having a conventional semi-conductor wafer polishing pad 23 disposed thereon. Workpiece, for example, semi-conductor wafer 7 is suspended over pad 23 from carrier 5, which is rotated by quill drive motor 3. Slurry dispenser 11 dispenses slurry upon the surface of polishing pad 23 through elongated tube 9. Rotating wafer 7 is lowered into contact with rotating pad 23 to perform CMP in a conventional manner.

Apparatus 1 further includes elongated pipe 17 having holes 19 formed therethrough and linked via a flexible tube to compressed air supply 21. Air from supply 21 is directed to the surface of pad 23 through holes 19, and serves to blow away the polishing products which may be trapped by the pad fibers, and to reduce the matting of the pad. Air supply 21 preferably is used for CMP of a metal layer. All of the above-described structure is conventional and is shown, for example, in the above-discussed patent to Cote et at. Alternatively, for CMP of an oxide layer with a slurry including cerium, it is preferred to replace air supply 21 with a nylon brush. Other suitable conventional mechanisms for performing CMP on wafers are shown in U.S. Pat. No. 5,069,002 to Sandhu et at, and U.S. Pat. No. 4,481,741 to Bouladon et al, both of which are incorporated by reference. The choice of slurry and polishing pad will depend upon the type of polishing which is being performed.

Apparatus 1 further includes conventional X-ray emitting tube 32 and conventional X-ray spectrometer 30. For example, suitable tubes 32 and spectrometers 30 are sold by Rigaku. Tube 32 and spectrometer 30 are mounted above pad 23. Though not shown, the manner in which tube 32 and spectrometer 30 would be mounted would be conventional, for example, by brackets. X-ray tube 32 is angled so as to emit an X-ray beam upon a surface of pad 23 which is not covered by wafer holder 5 during CMP. X-ray spectrometer 30 is mounted at a corresponding angle so as to receive the X-ray fluorescence from pad 23 which results from the beam emitted by tube 32 illuminating pad 23. Spectrometer 30 measures the intensity in counts per second at the given frequency of fluorescence. The intensity is dependent upon the slurry which is disposed upon pad 23, and in particular, the density of the suspended particles in the liquid. The frequency at which X-ray fluorescence occurs for a given slurry would be known to the skilled artisan. Accordingly, spectrometer 30 would be tuned to allow for detection of fluorescence having the expected frequency.

Calculating circuit 35 such as a microprocessor is coupled to X-ray spectrometer 30. Calculating circuit 35 is programmed to use a functional relationship between X-ray intensity and CMP rate to be described below to calculate CMP rate. Calculating circuit 35 is preferably coupled to an output device such as a visual display or a printer for the purpose of outputting the calculated CMP rate to an operator. Calculating circuit 35 may be, if desired, part of a control circuit for controlling the ON/OFF switching of X-ray emitter tube 32 and may be separate from or incorporated with control circuitry for controlling motors 3 and 15, dispenser 11 and air supply 21.

FIG. 6 is a graph showing the X-ray intensity in kilocounts/second expressed as a function of the density in mg/cm3 for a slurry consisting of 1 wt % Ceria (CeO2) suspended in 99 wt % water. Both pad 23 and carrier 5 were rotated at 100 rpm. Wafer 7 was pressed upon pad 23 with a downward pressure of 275 g/cm2. The distance between the center of wafer 7 and the center of pad 23 was 170 mm. The polishing pad was a SUBA-800 manufactured by Rodel. The density is measured in a conventional manner. For example, the pad would be removed and cut, and then dissolved in sulfuric acid (H2 SO4). Thereafter, the density would be determined by the inductively coupled plasma mass spectroscopy (ICP-mass) method. The functional relationship is generated by simultaneously measuring the intensity and density at a plurality of different times during CMP and extrapolating to obtain a correspondence between a given density and detected intensity. The graph of FIG. 6 was plotted based upon three different densities. As discussed further below, by once generating and making use of this functional correspondence, the CMP rate can be determined as well.

FIG. 5 is a graph of the CMP rate of a silicon oxide (SiO2) layer expressed in Å/min as a function of the Ceria density. At the same time that the graph of FIG. 6 was being generated by measuring the intensity at different densities, the CMP rate was determined by removal Of a test wafer and measuring the thickness to obtain the graph of FIG. 5. Although, as shown in FIG. 5, it is possible to obtain a direct measurement of the CMP rate as function of density, use of this functional relationship to determine the CMP rate requires use of the above-described ICP-mass method in which polishing pad 23 must be removed from the CMP apparatus, and dissolved in sulfuric acid (H2 SO4). However, once the procedure is performed, pad 23 cannot be used again. Even if the pad were reusable, the slurry would have to be replaced. In either case, the results of the analysis would be useless.

Accordingly, it is not practical to directly make use of the functional relationship shown in the graph of FIG. 5 to determine the CMP rate. However, since as shown in FIG. 6, there is a functional relationship between X-ray intensity and Ceria density, and since there is a functional relationship between the CMP rate and Ceria density as shown in FIG. 5, there must be a direct functional relations;hip between the X-ray intensity and the CMP rate. This functional relationship is shown in the graph of FIG. 7, which is a graph of CMP rate as a function of X-ray intensity. The functional relationship of FIG. 7 can be established by once determining the relationships shown in FIGS. 5 and 6 for a chosen combination of pad, slurry and chip layer. Thereafter, by use of calculating circuit 35, the X-ray intensity can be converted directly to a CMP rate by use of the plotted function.

Accordingly, for a given polishing pad, slurry and chip layer upon which CMP is to be applied, the present invention allows for the direct determination and display of the CMP rate. Since the emission of the X-ray beam and detection of the fluorescence does not require removal of the polishing pad or wafer, the CMP rate can be determined without interfering with the CMP process. Accordingly, the CMP rate can be determined without loss of time or destruction of a usable wafer. Further, the CMP rate may be determined instantaneously throughout the polishing process. Thus, any variation in the CMP rate which would affect whether the layers will have thickness variations within the accepted tolerances will be known immediately.

Knowledge of the CMP rate by the present invention allows for instantaneous adjustments to be made. If necessary, the CMP rate can be adjusted by changing the downward pressure or rotating speed of the wafer, pad or both. Further, the microprocessor can be programmed to continuously calculate the quantity of material removed by CMP by making use of the detected CMP rate and duration at which CMP is applied at that rate. The microprocessor can be programmed such that after it has been determined that a desired quantity of material has been removed, CMP is discontinued.

As shown, the graphs of FIGS. 5 and 6 were plotted based on measurements made at three different densities of Ceria. Accordingly, the graph of FIG. 7 also was based upon three measurements. The actual number of measurements needed will depend upon the tolerances needed for the particular layer being polished, and is left up to the skilled practitioner. Of course, the more measurements which are made, the greater the accuracy. Furthermore, the graphs of FIGS. 5-7 are based upon measurements made at the above-noted rotation rates of the pad and wafer, center of pad to center of wafer distance and wafer pressure. The CMP rate for a given density will vary with variations in these factors. By making measurements of the CMP rate v. density and X-ray intensity v. density for variations in these factors, the CMP rate can be known as a function of the intensity at different rotation rates, center to center distances and pressures.

The uniformity of the distribution of the Ceria on the pad and the uniformity of pad wear also affect the uniformity of polishing. By adjusting the angle of incidence of the X-ray beam, the polishing rate at different locations throughout the surface of the polishing pad can be known. For example, the beam can be moved in a radial direction along the pad, from the inner radial location (a) of the pad which contacts the wafer, to the outer radial location (b). Alternatively, the position of the beam can remain stationary, while the pad is slowly rotated so that the polishing rate at different locations along a constant pad radius can be determined. In either case, if deviations in the polishing rate are detected, and the deviations are beyond a threshold level, the pad can be reconditioned by removal of the embedded abrasive particles, or if necessary, discarded. These adjustments of the beam position could be performed by conventional motors.

Although the invention was described above with respect to polishing of a silicon oxide layer, it also is applicable to polishing of other layers, for example, tungsten layers. Furthermore, a similar relationship exists between the CMP rate and the quantity of material removed from the polished layer. In particular, both the CMP rate and X-ray intensity are functions of the density of removed SiO2 in the slurry. Accordingly, in the same manner as discussed above with respect to the density of the particles in the slurry, a graph can be plotted showing the CMP rate as a function of the X-ray intensity, with the graph calculated based upon the measured density of SiO2 in the slurry.

The relationship between X-ray fluorescence and the density of suspended particles in the slurry also can be used to determine the polishing end point during CMP. FIG. 8a shows a wafer including a layer of tungsten W disposed on a layer of SiO2 by a conventional technique. The SiO2 layer includes a trench which is filled with the tungsten. The wafer undergoes CMP, for example, with a slurry including Al2 O3 as an abrasive, to remove the tungsten from the SiO2 layer, with the exception of the material in the trench. FIG. 8b shows the wafer at the desired endpoint of CMP, in which the surface of the tungsten in the trench is substantially level with the surface of the SiO2, although as shown, in practice the tungsten layer in the trench may have a slightly concave surface.

FIG. 9 is a graph showing the density of the removed tungsten in the slurry as a function of time. At the initiation of CMP at time t0, there will be little or no tungsten in the slurry. As CMP proceeds, the tungsten initially will be removed at a rapid rate exceeding the rate at which the slurry is sprayed on the pad such that the density of the tungsten in the slurry will increase rapidly as well until time t1. Thereafter, a steady state of tungsten removal and spraying of slurry will be reached in which the density will remain substantially constant. At time t2, the tungsten layer covering the SiO2 will be substantially entirely removed. Thereafter, only the tungsten within the trench will be removed due to further polishing. At this point, the density of tungsten in the slurry will begin to drop rapidly.

Accordingly, the time at which the tungsten density begins to drop rapidly generally corresponds to the desired CMP endpoint. As discussed above, there will be a direct relationship between the X-ray fluorescence intensity and tungsten density, similar to the relationship shown in FIG. 6 for Ceria, with the intensity remaining constant when the density remains constant, and the intensity decreasing when the density decreases. Accordingly, by monitoring the fluorescence to determine when there is a sudden drop in intensity, the desired CMP endpoint can be detected. In practice, CMP could be terminated when the intensity undergoes a reduction to a level which is less than a predetermined level, or is decreased by greater than a predetermined rate. Furthermore, although this aspect of the invention is disclosed with respect to removal of a tungsten layer, it will also work for CMP of other layers, for example, polishing of a SiO2 layer with a slurry including CeO2 as the abrasive particles. In this type of polishing the density of silicon in the slurry would be detected.

Though the above invention has been described for one particular slurry, polishing pad and layer upon which CMP is being applied, it should be understood that the invention is broadly applicable to any particular slurry, pad and surface to be polished. Thus, the invention has broad applicability to all CMP polishing techniques.

This invention has been described in detail in connection with the preferred embodiments. These embodiments, however, are merely for example only and the invention is not restricted thereto. It will be understood by those skilled in the art that other variations and modifications can easily be made within the scope of this invention as defined by the claims.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US4417355 *Jan 8, 1981Nov 22, 1983Leningradskoe Npo "Burevestnik"X-Ray fluorescence spectrometer
US5069002 *Apr 17, 1991Dec 3, 1991Micron Technology, Inc.Apparatus for endpoint detection during mechanical planarization of semiconductor wafers
US5081796 *Aug 6, 1990Jan 21, 1992Micron Technology, Inc.Method and apparatus for mechanical planarization and endpoint detection of a semiconductor wafer
US5113421 *May 12, 1989May 12, 1992Data Measurement CorporationMethod and apparatus for measuring the thickness of a coating on a substrate
US5196353 *Jan 3, 1992Mar 23, 1993Micron Technology, Inc.Method for controlling a semiconductor (CMP) process by measuring a surface temperature and developing a thermal image of the wafer
US5222329 *Mar 26, 1992Jun 29, 1993Micron Technology, Inc.Acoustical method and system for detecting and controlling chemical-mechanical polishing (CMP) depths into layers of conductors, semiconductors, and dielectric materials
US5240552 *Dec 11, 1991Aug 31, 1993Micron Technology, Inc.Chemical mechanical planarization (CMP) of a semiconductor wafer using acoustical waves for in-situ end point detection
US5245794 *Apr 9, 1992Sep 21, 1993Advanced Micro Devices, Inc.Audio end point detector for chemical-mechanical polishing and method therefor
US5265378 *Jul 10, 1992Nov 30, 1993Lsi Logic CorporationDetecting the endpoint of chem-mech polishing and resulting semiconductor device
US5280176 *Nov 6, 1992Jan 18, 1994The United States Of America As Represented By The Secretary Of CommerceX-ray photoelectron emission spectrometry system
US5308438 *Jan 30, 1992May 3, 1994International Business Machines CorporationProviding a polishing pad coated with a slurry, rotating workpiece on pad, controlling rotational speed of workpiece and applying pressure, and monitoring current drawn by motor
US5362969 *Apr 23, 1993Nov 8, 1994Luxtron CorporationProcessing endpoint detecting technique and detector structure using multiple radiation sources or discrete detectors
US5399229 *May 13, 1993Mar 21, 1995Texas Instruments IncorporatedSystem and method for monitoring and evaluating semiconductor wafer fabrication
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5609718 *Nov 20, 1995Mar 11, 1997Micron Technology, Inc.Method and apparatus for measuring a change in the thickness of polishing pads used in chemical-mechanical planarization of semiconductor wafers
US5667424 *Sep 25, 1996Sep 16, 1997Chartered Semiconductor Manufacturing Pte Ltd.New chemical mechanical planarization (CMP) end point detection apparatus
US5698455 *Feb 9, 1995Dec 16, 1997Micron Technologies, Inc.Method for predicting process characteristics of polyurethane pads
US5733171 *Jul 18, 1996Mar 31, 1998Speedfam CorporationApparatus for the in-process detection of workpieces in a CMP environment
US5733176 *May 24, 1996Mar 31, 1998Micron Technology, Inc.Polishing pad and method of use
US5801066 *Mar 6, 1997Sep 1, 1998Micron Technology, Inc.Method and apparatus for measuring a change in the thickness of polishing pads used in chemical-mechanical planarization of semiconductor wafers
US5823853 *Jan 9, 1997Oct 20, 1998Speedfam CorporationApparatus for the in-process detection of workpieces with a monochromatic light source
US5834377 *Apr 7, 1997Nov 10, 1998Industrial Technology Research InstituteIn situ method for CMP endpoint detection
US5834642 *Jul 25, 1997Nov 10, 1998International Business Machines CorporationDownstream monitor for CMP brush cleaners
US5930586 *Jul 3, 1997Jul 27, 1999Motorola, Inc.Method and apparatus for in-line measuring backside wafer-level contamination of a semiconductor wafer
US5949927 *Mar 9, 1995Sep 7, 1999Tang; Wallace T. Y.In-situ real-time monitoring technique and apparatus for endpoint detection of thin films during chemical/mechanical polishing planarization
US5969805 *Nov 4, 1997Oct 19, 1999Micron Technology, Inc.Method and apparatus employing external light source for endpoint detection
US5974868 *Aug 20, 1998Nov 2, 1999International Business Machines CorporationDownstream monitor for CMP brush cleaners
US5993289 *Mar 5, 1998Nov 30, 1999Speedfam-Ipec CorporationMethods for the in-process detection of workpieces in a CMP environment
US6010538 *Jan 11, 1996Jan 4, 2000Luxtron CorporationIn situ technique for monitoring and controlling a process of chemical-mechanical-polishing via a radiative communication link
US6015333 *Aug 17, 1998Jan 18, 2000Lucent Technologies Inc.Method of forming planarized layers in an integrated circuit
US6045434 *Nov 10, 1997Apr 4, 2000International Business Machines CorporationMethod and apparatus of monitoring polishing pad wear during processing
US6060370 *Jun 16, 1998May 9, 2000Lsi Logic CorporationMethod for shallow trench isolations with chemical-mechanical polishing
US6066266 *Jul 8, 1998May 23, 2000Lsi Logic CorporationIn-situ chemical-mechanical polishing slurry formulation for compensation of polish pad degradation
US6069081 *Apr 28, 1995May 30, 2000International Buiness Machines CorporationTwo-step chemical mechanical polish surface planarization technique
US6071818 *Jun 30, 1998Jun 6, 2000Lsi Logic CorporationEndpoint detection method and apparatus which utilize an endpoint polishing layer of catalyst material
US6074517 *Jul 8, 1998Jun 13, 2000Lsi Logic CorporationMethod and apparatus for detecting an endpoint polishing layer by transmitting infrared light signals through a semiconductor wafer
US6077783 *Jun 30, 1998Jun 20, 2000Lsi Logic CorporationMethod and apparatus for detecting a polishing endpoint based upon heat conducted through a semiconductor wafer
US6080670 *Aug 10, 1998Jun 27, 2000Lsi Logic CorporationMethod of detecting a polishing endpoint layer of a semiconductor wafer which includes a non-reactive reporting specie
US6108093 *Jun 4, 1997Aug 22, 2000Lsi Logic CorporationAutomated inspection system for residual metal after chemical-mechanical polishing
US6115233 *Jun 28, 1996Sep 5, 2000Lsi Logic CorporationIntegrated circuit device having a capacitor with the dielectric peripheral region being greater than the dielectric central region
US6117779 *Dec 15, 1998Sep 12, 2000Lsi Logic CorporationEndpoint detection method and apparatus which utilize a chelating agent to detect a polishing endpoint
US6120349 *Jun 26, 1997Sep 19, 2000Canon Kabushiki KaishaPolishing system
US6121147 *Dec 11, 1998Sep 19, 2000Lsi Logic CorporationApparatus and method of detecting a polishing endpoint layer of a semiconductor wafer which includes a metallic reporting substance
US6126511 *Jul 19, 1999Oct 3, 2000Sony CorporationPolishing device and correcting method therefor
US6136043 *Apr 20, 1999Oct 24, 2000Micron Technology, Inc.Forming an elastomeric material into a polishing pad having a planar surface; and dyeing pad with at least one dye to color the elastomeric material with a color that extends from the planar surface to a pad depth; use in determining wear life
US6179956Nov 16, 1999Jan 30, 2001Lsi Logic CorporationMethod and apparatus for using across wafer back pressure differentials to influence the performance of chemical mechanical polishing
US6194231Mar 1, 1999Feb 27, 2001National Tsing Hua UniversityMethod for monitoring polishing pad used in chemical-mechanical planarization process
US6201253Oct 22, 1998Mar 13, 2001Lsi Logic CorporationMethod and apparatus for detecting a planarized outer layer of a semiconductor wafer with a confocal optical system
US6234883Oct 1, 1997May 22, 2001Lsi Logic CorporationMethod and apparatus for concurrent pad conditioning and wafer buff in chemical mechanical polishing
US6241847Jun 30, 1998Jun 5, 2001Lsi Logic CorporationPolishing semiconductor wafers with slurry that allows an infrared spectrum to be emitted through detects rate of change of intensity level and generates control signal
US6256094Dec 30, 1999Jul 3, 2001Micron Technology, Inc.Method and apparatus for automated, in situ material detection using filtered fluoresced, reflected, or absorbed light
US6258205Mar 24, 2000Jul 10, 2001Lsi Logic CorporationEndpoint detection method and apparatus which utilize an endpoint polishing layer of catalyst material
US6268224Jun 30, 1998Jul 31, 2001Lsi Logic CorporationMethod and apparatus for detecting an ion-implanted polishing endpoint layer within a semiconductor wafer
US6285035Jul 8, 1998Sep 4, 2001Lsi Logic CorporationApparatus for detecting an endpoint polishing layer of a semiconductor wafer having a wafer carrier with independent concentric sub-carriers and associated method
US6287171 *Feb 15, 2000Sep 11, 2001Speedfam-Ipec CorporationSystem and method for detecting CMP endpoint via direct chemical monitoring of reactions
US6322600Apr 22, 1998Nov 27, 2001Advanced Technology Materials, Inc.Planarization compositions and methods for removing interlayer dielectric films
US6326305 *Dec 5, 2000Dec 4, 2001Advanced Micro Devices, Inc.Controlling candida, cryptococcus, aspergillus infections
US6338668 *Aug 16, 2000Jan 15, 2002Taiwan Semiconductor Manufacturing Company, LtdIn-line chemical mechanical polish (CMP) planarizing method employing interpolation and extrapolation
US6340434Sep 3, 1998Jan 22, 2002Lsi Logic CorporationMethod and apparatus for chemical-mechanical polishing
US6354908Jan 4, 2001Mar 12, 2002Lsi Logic Corp.Method and apparatus for detecting a planarized outer layer of a semiconductor wafer with a confocal optical system
US6369887Apr 25, 2001Apr 9, 2002Micron Technology, Inc.Method and apparatus for automated, in situ material detection using filtered fluoresced, reflected, or absorbed light
US6375791Dec 20, 1999Apr 23, 2002Lsi Logic CorporationMethod and apparatus for detecting presence of residual polishing slurry subsequent to polishing of a semiconductor wafer
US6383332May 31, 2000May 7, 2002Lsi Logic CorporationFor semiconductors
US6424019Feb 18, 2000Jul 23, 2002Lsi Logic CorporationShallow trench isolation chemical-mechanical polishing process
US6429928Sep 20, 1999Aug 6, 2002Micron Technology, Inc.Method and apparatus employing external light source for endpoint detection
US6440319 *Aug 16, 2000Aug 27, 2002Micron Technology, Inc.Method and apparatus for predicting process characteristics of polyurethane pads
US6466642 *Jun 2, 2000Oct 15, 2002Speedfam-Ipec CorporationMethods and apparatus for the in-situ measurement of CMP process endpoint
US6503124 *Nov 16, 2000Jan 7, 2003Taiwan Semiconductor Manufacturing CompanyMethod for endpoint detection for copper CMP
US6509960Feb 28, 2001Jan 21, 2003Micron Technology, Inc.Generating signal indicative of intensity of emanated light
US6514775Nov 9, 2001Feb 4, 2003Kla-Tencor Technologies CorporationIn-situ end point detection for semiconductor wafer polishing
US6517413 *Oct 25, 2000Feb 11, 2003Taiwan Semiconductor Manufacturing CompanyMethod for a copper CMP endpoint detection system
US6517668 *Jul 20, 2001Feb 11, 2003Micron Technology, Inc.Method and apparatus for endpointing a chemical-mechanical planarization process
US6528389Dec 17, 1998Mar 4, 2003Lsi Logic CorporationSubstrate planarization with a chemical mechanical polishing stop layer
US6531397Jan 9, 1998Mar 11, 2003Lsi Logic CorporationMethod and apparatus for using across wafer back pressure differentials to influence the performance of chemical mechanical polishing
US6562182Jul 20, 2001May 13, 2003Micron Technology, Inc.Method and apparatus for endpointing a chemical-mechanical planarization process
US6579799Sep 25, 2001Jun 17, 2003Micron Technology, Inc.Method and apparatus for controlling chemical interactions during planarization of microelectronic substrates
US6614529Dec 28, 1992Sep 2, 2003Applied Materials, Inc.In-situ real-time monitoring technique and apparatus for endpoint detection of thin films during chemical/mechanical polishing planarization
US6617178 *Jul 2, 2002Sep 9, 2003Agilent Technologies, IncTest system for ferroelectric materials and noble metal electrodes in semiconductor capacitors
US6628397Sep 15, 1999Sep 30, 2003Kla-TencorApparatus and methods for performing self-clearing optical measurements
US6629879 *May 8, 2001Oct 7, 2003Advanced Micro Devices, Inc.Method of controlling barrier metal polishing processes based upon X-ray fluorescence measurements
US6671051Apr 24, 2000Dec 30, 2003Kla-TencorApparatus and methods for detecting killer particles during chemical mechanical polishing
US6704107Nov 4, 1997Mar 9, 2004Micron Technology, Inc.Method and apparatus for automated, in situ material detection using filtered fluoresced, reflected, or absorbed light
US6752689 *Jul 5, 2001Jun 22, 2004Nova Measuring Instruments Ltd.Apparatus for optical inspection of wafers during polishing
US6776871Jul 20, 2001Aug 17, 2004Micron Technology, Inc.Method and apparatus for endpointing a chemical-mechanical planarization process
US6831734Mar 7, 2002Dec 14, 2004Micron Technology, Inc.Method and apparatus for automated, in situ material detection using filtered fluoresced, reflected, or absorbed light
US6849152Jul 19, 2001Feb 1, 2005Applied Materials, Inc.In-situ real-time monitoring technique and apparatus for endpoint detection of thin films during chemical/mechanical polishing planarization
US6857434 *Jan 24, 2002Feb 22, 2005International Business Machines CorporationCMP slurry additive for foreign matter detection
US6991514Feb 21, 2003Jan 31, 2006Verity Instruments, Inc.Optical closed-loop control system for a CMP apparatus and method of manufacture thereof
US7024063Jan 25, 2005Apr 4, 2006Applied Materials Inc.In-situ real-time monitoring technique and apparatus for endpoint detection of thin films during chemical/mechanical polishing planarization
US7037403Aug 14, 1998May 2, 2006Applied Materials Inc.In-situ real-time monitoring technique and apparatus for detection of thin films during chemical/mechanical polishing planarization
US7052364 *Jun 14, 2004May 30, 2006Cabot Microelectronics CorporationReal time polishing process monitoring
US7102737Jun 4, 2004Sep 5, 2006Micron Technology, Inc.Method and apparatus for automated, in situ material detection using filtered fluoresced, reflected, or absorbed light
US7121919 *Aug 30, 2001Oct 17, 2006Micron Technology, Inc.Chemical mechanical polishing system and process
US7169015Jun 4, 2004Jan 30, 2007Nova Measuring Instruments Ltd.Apparatus for optical inspection of wafers during processing
US7569119Feb 21, 2006Aug 4, 2009Applied Materials, Inc.In-situ real-time monitoring technique and apparatus for detection of thin films during chemical/mechanical polishing planarization
US7582183Oct 24, 2007Sep 1, 2009Applied Materials, Inc.Apparatus for detection of thin films during chemical/mechanical polishing planarization
US7751609Apr 20, 2000Jul 6, 2010Lsi Logic CorporationDetermination of film thickness during chemical mechanical polishing
US8595296Dec 17, 2007Nov 26, 2013Open Invention Network, LlcMethod and apparatus for automatically data streaming a multiparty conference session
US8688189May 17, 2005Apr 1, 2014Adnan ShennibProgrammable ECG sensor patch
US20130244359 *Oct 27, 2011Sep 19, 2013Pilkington Group LimitedPolishing coated substrates
DE102005037354A1 *Aug 8, 2005Oct 5, 2006Fujitsu Ltd., KawasakiRöntgenstrahlfluoreszenzanalysator, Röntgenstrahlfluoreszenzanalyseverfahren, und Röntgenstrahlfluoreszenzanalyseprogramm
EP0823309A1 *Aug 6, 1997Feb 11, 1998MEMC Electronic Materials, Inc.Method and apparatus for controlling flatness of polished semiconductor wafers
EP1060835A2 *Aug 6, 1997Dec 20, 2000MEMC Electronic Materials, Inc.Method and apparatus for controlling flatness of polished semiconductor wafers
WO1996024839A2 *Jan 30, 1996Aug 15, 1996Micron Technology IncMethod and apparatus for predicting process characteristics of polyurethane pads
WO1997025660A1 *Dec 16, 1996Jul 17, 1997Luxtron CorpIn situ technique for monitoring and controlling a process of chemical-mechanical-polishing via a radiative communication link
WO2006089291A1 *Feb 21, 2006Aug 24, 2006Neopad Technologies CorpUse of phosphorescent materials for two-dimensional wafer mapping in a chemical mechanical polishing
Classifications
U.S. Classification438/16, 257/E21.304, 451/8, 451/6, 438/693, 378/50, 378/44
International ClassificationH01L21/304, H01L21/66, B24B37/00, H01L21/321, B24B37/04
Cooperative ClassificationH01L21/3212, B24B37/005
European ClassificationB24B37/005, H01L21/321P2
Legal Events
DateCodeEventDescription
Jun 15, 2007FPAYFee payment
Year of fee payment: 12
Jun 17, 2003FPAYFee payment
Year of fee payment: 8
Jun 28, 1999FPAYFee payment
Year of fee payment: 4
Feb 1, 1995ASAssignment
Owner name: KABUSHIKI KAISHA TOSHIBA, JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:YANO, HIROYUKI;OKUMURA, KATSUYA;REEL/FRAME:007337/0533
Effective date: 19941212